1. Field of the Invention
This invention relates generally to devices for the acquisition of electroencephalographic (EEG) signals, and more particularly concerns an electrode locator device that can be applied by a user without assistance for acquiring high quality EEG signals, and is comfortable and cosmetically acceptable for use during daily activities.
2. Description of Related Art
Advances in detection and characterization of electroencephalographic (EEG) signals from the brain have allowed EEG monitoring to be useful in analysis of neurological disorders, and laboratory studies of awareness and sleep. Recent advances have, for example, provided much information about the correlation between EEG signals and an individual""s level of arousal, in a continuum from vigilance to drowsiness, and sleep onset. Devices for monitoring EEG signals are typically used in a laboratory environment or in a home for sleep studies, but are typically set up and operated by trained technicians. Shifts in EEG signals have been directly correlated with changes in performance, particularly during tasks which require sustained attention over prolonged periods of time. However, application of EEG monitoring to environments for study and monitoring of brain performance, such as for monitoring brain activity in the home, office, aircraft cockpit, and train or truck operations cabins, for example, has been severely hampered by cumbersome detection and recording equipment, and the need for the assistance of a technician typically required to obtain high quality data.
In fitting EEG electrodes to the scalp of a subject being monitored, an EEG technician will typically first measure the distances between the nasium and the occipital bone, and between the mastoid processes, to identify the top center (Cz) of the head, and will then position all other electrodes relative to these landmarks to comply with the International 10/20 System that is well known in the art as the standard for positioning of EEG electrodes. The technician will then part the hair of the scalp of the subject at the intended electrode sites, clean the electrode sites to remove dirt, hair oil, and the like, and prepare the scalp to remove the top layer of dead skin, to ensure that low scalp-electrode impedance values are obtained.
Conventionally, after preparation of the intended electrode sites on the scalp, electrodes are glued to the scalp with collodion, typically a viscous solution of pyroxilin, a commercially available nitrocellulose, in ether and alcohol, that is a particularly noxious preparation that can bond with the scalp and hair, to provide a stable scalp-electrode interface, until dissolved by a solvent such as acetone, or a non-acetone, oil based collodion remover.
A variety of hats, caps, helmets and headgear are known that have been developed to position EEG electrodes according to the International 10/20 System and provide a scalp-electrode interface without the use of an adhesive such as collodion. However, these types of devices are commonly uncomfortable and unacceptable for use during activities of work and daily living. One such sleep monitoring headgear utilizes a circumferential elastic headband to generate an electrode seating pressure for a single electrode located at the top center of the head of a subject. It has been found, however, that when such a circumferential elastic headband is utilized to seat multiple electrodes, the headband slides up and posteriorly on the forehead.
Such conventional hats, caps, helmets and headgear also typically make it difficult for a user to part the hair or abrade their scalp at the electrode site without assistance. Particularly where disposable electrodes are used that are not to be bonded to the scalp of the user to provide an electrode-scalp interface, the placement of an electrode over hair can increase the impedance between the electrode and scalp, causing significant signal artifacts if the hair slides or is pulled across the surface of the electrode while signals are being acquired. One such conventional device requires the technician to lift or turn a disposable electrode on its side after a conductive gel on the electrode has made contact with the hair of the scalp, in order to part the hair at the intended area of the scalp for placement of the electrode. Several systems used in the laboratory for non-ambulatory EEG monitoring dispense electrode gel to the electrode, but would make an EEG electrode locator headgear uncomfortably heavy and inconvenient for ambulatory use outside a laboratory environment. Another type of device utilizes sharp tipped metal points to penetrate the dead layer of skin. However, such sharp metal points can pose a medical danger due to the potential for infection, particularly with repeated abrasions, and the possibility of penetration of the skull if the device were to be struck accidentally during ambulatory activity, or other activities during daily living.
It would therefore be desirable to provide an EEG electrode locator headgear that utilizes electrode locators to identify electrode sites, and gives the user access for application of electrodes to the electrode sites, permitting conventional scalp preparation techniques, such as application of abrasion cream with a xe2x80x9cQ-tipxe2x80x9d, for example, to be applied by the user without technical assistance. It would also be desirable to provide an EEG electrode locator headgear utilizing a device allowing a user the option of preparing an intended electrode site on the scalp by parting of the hair, prior to seating of the electrodes, and for placement of electrodes. While prior EEG electrode locating techniques typically required a technician to accurately locate electrodes, it would be desirable to provide an EEG electrode locator headgear that utilizes a locating device that can be positioned by the user over a prominent location on the scalp of the user, such as over the occipital bone, or over the nasium, to orient the headgear and confirm accurate placement of the EEG electrodes. The present invention meets these needs.
Briefly, and in general terms, the present invention provides for an EEG electrode locator headgear for a user that allows the user to locate and apply disposable EEG electrodes accurately according to the International 10/20 System without technical assistance, to allow the acquisition of high quality EEG signals. The EEG electrode locator headgear is portable and comfortable, allowing it to be worn by the user during daily activities as one would a cap or visor. The headgear provides a stable electrode-scalp interface for a plurality of electrodes without covering the entire head, and without requiring a chin strap for normal adult usage, and allows the hair to be parted and optionally preparation of the scalp by the user without technical assistance.
The invention accordingly provides for an electroencephalograph (EEG) electrode locator headgear including a front pad of material having first and second ends, the front pad of material being adapted to extend across a user""s forehead, a base strap assembly having a first end connected to the first end of the front pad of material, and a second end connected to the second end of the front pad of material, the front pad of material and the base strap assembly being adapted to be secured comfortably around the circumference of a user""s head, a plurality of EEG electrode locators adapted to receive EEG electrodes, and a plurality of locator straps connected to the front pad of material, the base strap assembly, and to the plurality of EEG electrode locators for accurately positioning the plurality of EEG electrode locators positioned relative to the scalp of a user.
In a presently preferred embodiment, the front pad of material includes a visor or front bill attached to the front pad of material, which is typically non-elastic. The base strap assembly is preferably adjustable, and in a presently preferred aspect comprises a pair of adjustable elastic straps connected at one end to the front pad of material and adjustably connected together at the other end. The base strap may also advantageously include an occipital locator device adapted to be seated on a region of the user""s scalp over the user""s occipital bone, with the base strap assembly including first and second elastic edge straps connected at one end to the front pad of material, and adjustably connected at the other end to the occipital locator device. The occipital locator device preferably has a plurality of feet adapted to be positioned over the user""s occipital bone. In an alternative preferred embodiment, an anterior locator strap having a free end adapted to be positioned over the user""s nasium can be connected to the front pad of material, to allow the user to confirm accurate placement of the electrode locators.
In another presently preferred aspect of the invention, the EEG electrode locators each comprise a hollow tubular base adapted to receive an EEG electrode, and an annular flange extending from an upper edge of the hollow tubular base, with the annular flange including a plurality of slots for receiving a plurality of the locator straps. In another presently preferred aspect, the hollow tubular base includes an EEG electrode locator electrical conductor adapted to be electrically connected to an EEG electrode inserted in the hollow tubular base of the EEG electrode locator, and intermediate electrical conductors are electrically connected to the EEG electrode locator electrical conductors and are adapted to be connected to an EEG monitor. In a presently preferred embodiment, three EEG electrode locators are provided, adapted to be positioned at a central (Cz) position, a parietal (Pz) position, and an occipital (Oz) position, relative to the scalp of a user. Alternatively, additional electrode locators may be provided for positioning additional electrodes according to the International 10/20 system.
In another presently preferred aspect of the invention, the plurality of locator straps are made of elastic material, such that the locator straps bias the plurality of EEG electrode locators, and thereby the electrodes inserted into the electrode locators, with a biasing pressure toward the user""s scalp, to provide a stable electrode-scalp interface capable of producing a high signal quality. A plurality of electrodes are also provided that are adapted to be seated in the plurality of electrode locators, respectively. As noted above, at least three electrodes are provided, although the electrode headgear can be adapted to accept more or fewer than three EEG electrodes, as desired. The electrodes are preferably disposable.
A plunger assembly is also preferably provided that is adapted to cooperate with the plurality of electrode locators either prior to or in conjunction with insertion of the EEG electrodes. The plunger assembly includes a hollow tubular base having an upper portion and a lower portion, and a plunger adapted to be received in the hollow tubular base. The plunger assembly is adapted to be inserted in the electrode locators to prepare the scalp of the user and to seat the electrodes.
The lower portion of the hollow tubular base advantageously includes a plurality of flexible, resilient fingers having distal ends that are biased to meet at a common distal central location, and that can be spread in order to part the hair of the scalp of the user at a desired site on the scalp of the user in preparation of the site for receiving an EEG electrode. The flexible, resilient fingers on the hollow tubular base of the plunger assembly are presently preferably plastic. The distal flexible, resilient fingers of the plunger hollow tubular base can be spread by insertion of an electrode through the plunger hollow tubular base, so that the plunger assembly can be used to simultaneously part the hair by spreading of the distal fingers of the plunger hollow tubular base, and seat the disposable electrode, and optionally also may be used to abrade the scalp of the user at the intended location of the electrode, such as by manually twisting the hollow tubular base to rub the distal ends of the distal fingers against the scalp of the user. The plunger is adapted to be inserted in the hollow tubular base of the plunger assembly to spread the distal flexible, resilient fingers.
In one presently preferred alternate embodiment, the plunger has an external helical rib, and the hollow tubular base has a corresponding interior groove for receiving and guiding the external helical rib of the plunger as the plunger is inserted in the hollow tubular base of the plunger assembly, to provide a predetermined turning and torque to the plunger as it is inserted. In another presently preferred aspect, the hollow tubular base of the plunger assembly includes an electrical conductor adapted to be electrically connected between an electrode inserted in the hollow tubular base and one of the electrode locators for conducting EEG signals from the electrodes to an EEG monitor.
In a second preferred embodiment, the invention provides for an electroencephalograph (EEG) electrode locator headgear comprising a base strap assembly adapted to be secured comfortably around the circumference of a user""s head, an elastic, stretchable cap portion connected to the plurality of EEG electrode locators, and a plurality of EEG electrode locators mounted to the elastic, stretchable cap portion for accurately positioning the plurality of EEG electrode locators relative to the user""s scalp, and for biasing the plurality of electrode locators toward the user""s scalp. A plurality of EEG electrodes are also provided that are adapted to be received in and cooperate with the plurality of EEG electrode locators, respectively. Each of the EEG electrodes includes a plunger assembly adapted to optionally prepare the user""s scalp and to seat the electrode in one of the EEG electrode locators. The plunger assembly includes a plunger member having an electrically conductive spreader member mounted to the lower end of the plunger member, and the spreader member advantageously includes a plurality of flexible, resilient fingers having distal ends biased to meet at a common distal central location. The plunger assembly preferably comprises an electrical conductor mounted to the plunger member adapted and electrically connected between the electrically conductive spreader member and the EEG electrode locator for conducting EEG signals from the electrodes to an EEG monitor. The flexible, resilient fingers are adapted to spread apart by exertion of downward pressure of the plunger assembly against the user""s scalp, so as to part the hair of the user""s scalp, for preparation of the scalp for effective contact by the electrodes. The plunger is preferably adapted to be inserted in the electrode locator to spread the distal flexible, resilient fingers, and the plunger assembly can be used to abrade the users scalp at the intended location of the electrode by manually twisting the plunger assembly to rub the distal ends of the distal fingers against the user""s scalp. In one presently preferred aspect, the plunger assembly comprises a cap connected to the upper portion of the plunger member. In order to improve the comfort of the user in applying the electrodes to the user""s scalp, the spreader member preferably comprises an electrically conductive cushion portion located between the flexible, resilient fingers adapted to rest against the user""s scalp after the electrode has been pressed downward to seat the electrode on the user""s scalp and spread the flexible, resilient fingers, to cushion the pressure of the electrode on the user""s scalp for additional comfort, and a conductive gel may also be disposed adjacent to the cushion portion of the spreader member and between the flexible, resilient fingers.
In a presently preferred aspect, the elastic, stretchable cap portion comprises one or more elastic locator straps connected to the plurality of EEG electrode locators, and preferably comprises a plurality of elastic locator straps, which can be made of elastic material, such as an elasticized fabric. The plurality of EEG electrode locators each comprise a plurality of slots for receiving the locator straps. In another presently preferred aspect, the elastic, stretchable cap portion comprises a stretch mesh cap of elastic, fabric material. An outer cap shell can optionally be further disposed over the elastic, stretchable cap portion, and may include shielding.
In another currently preferred aspect of the invention, the base strap assembly comprises a front pad of material adapted to extend across a user""s forehead, and a visor or front bill of the headgear may also attached to the front pad of material. The base strap assembly is currently preferably adjustable, and in one presently preferred embodiment comprises a pair of adjustable elastic straps connected at one end to the front pad of material and adjustably connected together at the other end. The base strap assembly may also further comprise an occipital locator device adapted to be seated on a region of the user""s scalp over the user""s occipital bone.
In the second embodiment, each of the electrode locators preferably includes an electrical conductor adapted to be electrically connected to one of the EEG electrodes inserted in the electrode locator, and in a presently preferred aspect, the electrode locator electrical conductor comprises a plurality of electrically conductive spring connectors. In a preferred embodiment, a circuit board base member is mounted to the electrode locator electrical conductor, and the plurality of electrically conductive spring connectors are mounted to the circuit board base member. In another preferred aspect, the electrode locators include spring loaded detent pins for engagement with the electrode, and the plunger member preferably has a plurality of grooves or ratchet strips for engagement with the corresponding spring loaded detent pins for seating the plunger assembly in the electrode locators.
In another presently preferred aspect of the second embodiment, the EEG electrode locator headgear further comprises an operational pre-amplifier electrically connected to the electrode locator electrical conductor to receive EEG signals from the electrode, and the EEG signals from the electrode locators are conducted from the pre-amplifier to an analog to digital converter mounted on the EEG electrode locator headgear. An RF transmitter is preferably connected to receive output from the analog to digital converter, for communicating digital EEG signals to an apparatus for analyzing the digital EEG signals from the user, which preferably comprises a data processing unit for also providing feedback to the user. In a presently preferred aspect, the data processing unit is battery powered, and includes a speaker for transmitting audio alert messages to the user. In another presently preferred aspect, the RF transmitter of the EEG electrode locator headgear is a bi-directional RF transmitter-receiver for receiving feedback signals from the apparatus for analyzing the digital EEG signals from the user, and a speaker is mounted in the EEG electrode locator headgear for communicating audio messages from the data processing unit. Storage means may also be mounted in the EEG electrode locator headgear for storing audio messages in analog format. In another preferred aspect, the outer cap shell of the EEG electrode locator headgear includes a Faraday shield to shield the pre-amplifiers from external noise and artifacts which may result from the use of the RF transmitter.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.